JP2023034254A - Method for processing single crystal silicon wafer - Google Patents

Abstract

To provide a wafer processing method capable of shortening processing time and reducing the probability of device breakage when a peeling layer is formed inside a wafer and then the wafer is separated with the peeling layer as a separation starting point.SOLUTION: A single crystal silicon wafer manufactured so that a specific crystal plane included in a crystal plane {100} (for example, crystal plane (100)) is exposed on each of the front and back surfaces of the wafer is irradiated with a laser beam along a first direction that is parallel to the specific crystal plane and forms an angle of 5° or less with respect to a specific crystal orientation included in a crystal orientation<100>(for example, crystal orientation [010]), thereby forming a peeling layer serving as a separation starting point between the front surface side and back surface side of the single crystal silicon wafer.SELECTED DRAWING: Figure 7

Description

The present invention relates to a single crystal silicon wafer processing method for forming a separation layer inside a single crystal silicon wafer and then separating the single crystal silicon wafer using the separation layer as a separation starting point.

Chips of semiconductor devices (hereinafter also simply referred to as "devices") are generally manufactured using disk-shaped single-crystal silicon wafers (hereinafter also simply referred to as "wafers"). Specifically, the wafer is partitioned into a plurality of regions by dividing lines set in a grid pattern, and devices are formed on the surface side of each region. Chips are manufactured by dividing this wafer along the planned division lines.

Further, a wafer may be provided with a through-silicon via (TSV) for the purpose of high integration of a package including a plurality of chips. In this package, for example, electrodes included in different chips can be electrically connected via TSVs.

For example, the TSVs are provided on the wafer in the following order. First, grooves are formed on the surface side of the wafer. This groove is then provided with a TSV. Next, the front side of the wafer is attached to the support wafer. The backside of the wafer is then ground until the TSVs are exposed on the backside of the wafer.

Here, in many cases, the outer peripheral region of the wafer is chamfered for the purpose of preventing cracks. Then, when the back side of the wafer having the chamfered outer peripheral region is ground until the thickness of the wafer is reduced to half or less, the back side of the outer peripheral region is shaped like a knife edge.

In this case, stress is concentrated on the back surface side of the outer peripheral region during grinding of the wafer, making the wafer more likely to crack, which may reduce the yield of chips obtained from the wafer. Therefore, it has been proposed to remove a portion of the outer peripheral region on the front side (so-called edge trimming) prior to grinding the back side of the wafer (see, for example, Patent Document 1).

As a result, the side surfaces of the wafer are substantially perpendicular to the front and back surfaces when the remainder of the outer peripheral region on the back surface side is removed by grinding. Therefore, stress concentration does not occur on the back surface side of the outer peripheral region during grinding of the wafer, and the wafer is less likely to crack. As a result, a decrease in chip yield can be suppressed.

However, when grinding the back side of the wafer until the TSV is exposed on the back side of the wafer after edge trimming, the amount of grinding of the wafer increases, and the amount of wear of the grindstone required for grinding the wafer increases. In this case, the cost of chips or packages manufactured using this wafer may increase, and the processing thereof may take a long time.

In view of this point, the focal point to be formed is positioned inside the wafer, and the wafer is irradiated with a laser beam having a wavelength that can pass through the wafer. A method of separating a wafer using a separation layer as a starting point of separation has been proposed (see, for example, Patent Document 2).

In this method, first, a laser beam is applied to a first ring-shaped region of the wafer where irregular reflection does not occur when irradiated with a laser beam (in other words, a ring-shaped region inside the chamfered outer peripheral region). to irradiate. As a result, a peeling layer (cylindrical peeling layer) serving as a separation starting point between the device-formed region and the peripheral region of the wafer is formed.

Next, the laser beam is applied to the second area of the wafer where irregular reflection does not occur when the laser beam is applied (in other words, the circular area inside the chamfered outer peripheral area). As a result, a peeling layer (disc-shaped peeling layer) serving as a separation starting point between the front surface side and the back surface side of the wafer is formed.

Then, by applying an external force to the wafer, the wafer is separated at the cylindrical release layer and the disk-shaped release layer. That is, the peripheral region of the wafer is separated from the region where the devices are formed, and the back side of the wafer is separated from the front side thereof.

When the wafer is separated in this way, it is possible to reduce the grinding amount of the wafer required until the TSV is exposed on the back surface of the wafer, and reduce the wear amount of the grindstone required for grinding this wafer. As a result, an increase in the cost of chips or packages manufactured using this wafer can be suppressed, and the time required for grinding the wafer can be shortened.

JP 2007-158239 A JP 2020-136442 A

The peeling layer described above is composed of a modified region in which the crystal structure of the single-crystal silicon constituting the wafer is disturbed, and cracks extending from the modified region. Specifically, when a wafer is irradiated with the laser beam described above, a modified region is formed inside the wafer centering on the focal point of the laser beam. Also, from this modified region, cracks extend along a predetermined crystal plane of the single-crystal silicon forming the wafer.

Here, single crystal silicon is generally most easily cleaved in a specific crystal plane included in the crystal plane {111}. For example, for a wafer manufactured such that a specific crystal plane included in the crystal plane {100} (for example, the crystal plane (100)) is exposed on each of the front and back surfaces, the crystal orientation <110> When a laser beam is irradiated along a crystal orientation (for example, crystal orientation [011]) parallel to a specific crystal plane exposed on each of the front and back surfaces of a wafer among specific crystal orientations, the crystal plane { 111}, many cracks extending along a specific crystal plane (for example, the crystal plane (111)) are generated.

Then, a specific crystal plane included in the crystal plane {100} of single crystal silicon (for example, the crystal plane (100)) and a specific crystal plane included in the crystal plane {111} (for example, the crystal plane (111)) The acute angle formed by is about 54.7°. Therefore, when the wafer is irradiated with the laser beam as described above, many cracks extending from the modified region in a direction inclined by about 54.7° with respect to the front surface or the rear surface of the wafer are generated.

That is, when the direction in which such cracks extend is decomposed into a component parallel (parallel component) and a component perpendicular (perpendicular component) to the front and back surfaces of the wafer, the perpendicular component becomes larger than the parallel component. Therefore, when a peeling layer (disc-shaped peeling layer) that serves as a separation starting point between the front side and the back side of the wafer is formed by irradiating the wafer with a laser beam as described above, the following problems arise. may occur.

First, in this case, since the parallel component in the direction in which the crack extends is relatively small, it is necessary to narrow the interval between the adjacent modified regions in order to connect the adjacent modified regions through the crack. When narrowing the interval between the adjacent modified regions, it is necessary to lengthen the processing time (laser beam irradiation time) required to form the disk-shaped peeling layer.

Moreover, in this case, since the vertical component in the direction in which the crack extends is relatively large, the crack may extend from the disk-shaped release layer toward the surface side of the wafer and damage the device. Although the possibility of device damage can be reduced by forming a disk-shaped release layer at a position sufficiently separated from the surface of the wafer, in this case, the amount of grinding increases when the wafer is subsequently ground. end up

In view of the above points, an object of the present invention is to shorten the processing time when separating the wafer using the peeling layer as a separation starting point after forming the peeling layer inside the wafer, and to reduce the probability of device damage. It is to provide a wafer processing method.

According to the present invention, it is manufactured so that specific crystal planes included in the crystal plane {100} are exposed on each of the front surface and the back surface, and a plurality of devices are formed on the front surface side and the outer peripheral region is chamfered. By irradiating a single-crystal silicon wafer with a laser beam having a wavelength that passes through the single-crystal silicon, the focal point to be formed is positioned inside the single-crystal silicon wafer. A method for processing a single crystal silicon wafer comprising forming a separation layer inside the crystalline silicon wafer and then separating the single crystal silicon wafer using the separation layer as a starting point for separation, wherein the surface side of the single crystal silicon wafer is supported. a bonding step of bonding to the front side of the wafer; and irradiating the laser beam from the back side of the single crystal silicon wafer to a first ring-shaped region inside the outer peripheral region of the single crystal silicon wafer. a first separation layer forming step of forming a first separation layer serving as a separation starting point between the region of the single crystal silicon wafer where the plurality of devices are formed and the peripheral region; By irradiating the laser beam from the rear surface side of the single crystal silicon wafer to the second region inside the outer peripheral region of the single crystal silicon wafer, the front surface side of the single crystal silicon wafer and the laser beam are irradiated. A second release layer forming step for forming a second release layer that serves as a starting point for separation from the back side, the bonding step, the first release layer forming step, and the second release layer forming step a separating step of separating the single crystal silicon wafer with the first separation layer and the second separation layer as starting points of separation by applying an external force to the single crystal silicon wafer after performing the separation step; In the second release layer forming step, in a first direction parallel to the specific crystal plane and forming an angle of 5° or less with respect to a specific crystal orientation included in the crystal orientation <100> A laser beam that irradiates a linear region along the first direction included in the second region with the laser beam while relatively moving the single crystal silicon wafer and the focal point along the an irradiating step, and the single crystal silicon in which the focal point is formed by the irradiation of the laser beam along a second direction parallel to the specific crystal plane and orthogonal to the first direction. The second release layer is formed by repeatedly performing an indexing step of moving the position inside the wafer. A method for processing a wafer is provided.

Further, the first release layer forming step is preferably performed before performing the second release layer forming step.

Moreover, it is preferable that the second region is located inside the first region.

Moreover, in the first peeling layer forming step, it is preferable that the first peeling layer is formed so as not to reach the back surface of the single crystal silicon wafer.

Further, in the first peeling layer forming step, the laser beam is irradiated so that the formed focal point is closer to the surface of the single crystal silicon wafer as it is closer to the outer peripheral region. One bottom surface is located on the surface side of the single crystal silicon wafer, and a second bottom surface having a smaller diameter than the first bottom surface is along the side surface of the truncated cone located inside the single crystal silicon wafer. Preferably, the second release layer is formed as follows.

In the present invention, a single crystal silicon wafer manufactured such that a specific crystal plane (for example, a crystal plane (100)) included in the crystal plane {100} is exposed on each of the front surface and the rear surface, and the specific and making an angle of 5° or less with respect to a specific crystal orientation (e.g., crystal orientation [010]) included in the crystal orientation <100> By irradiating with , a peeling layer (second peeling layer) that serves as a separation starting point between the front side and the back side of the single crystal silicon wafer is formed.

In this case, the crack extending from the modified region is more likely to be along the crystal plane {n10} (n is 10 or less) than along a specific crystal plane included in the crystal plane {111} (for example, the crystal plane (111)). (natural number of )) along a specific crystal plane (for example, the crystal plane (101)). The acute angle formed by the specific crystal plane included in the crystal plane {100} and the specific crystal plane included in the crystal plane {n10} is 45° or less.

Therefore, in the present invention, a single crystal silicon wafer manufactured so that a specific crystal plane included in the crystal plane {100} is exposed on each of the front surface and the back surface is parallel to the specific crystal plane. And, compared to the case where the second release layer is formed by irradiating a laser beam along a specific crystal orientation (for example, crystal orientation [011]) included in the crystal orientation <110> , the component parallel to the front and back surfaces of the wafer in the direction in which the crack extends (parallel component) increases, and the component perpendicular to it (perpendicular component) decreases.

As a result, in the present invention, the parallel component in the direction in which the crack extends increases, so the interval between adjacent modified regions can be lengthened. As a result, the movement distance (index) in the indexing feed step can be lengthened, and the processing time (laser beam irradiation time) can be shortened.

In addition, in the present invention, since the vertical component in the direction in which cracks extend is small, cracks are less likely to extend from the peel layer toward the surface side of the wafer. As a result, it is possible to reduce the probability that the device will be damaged when separating the front side and the back side of the wafer.

FIG. 1A is a top view schematically showing an example of a wafer, and FIG. 1B is a cross-sectional view schematically showing an example of a wafer. FIG. 2 is a flow chart schematically showing an example of a wafer processing method. FIG. 3 is a cross-sectional view schematically showing how the front side of the wafer is attached to the front side of the support wafer. FIG. 4 is a perspective view schematically showing an example of a laser processing apparatus. FIG. 5 is a diagram schematically showing how a laser beam travels in a laser beam irradiation unit. FIG. 6 is a partial cross-sectional side view schematically showing how a rotating wafer is irradiated with a laser beam. FIG. 7 is a flow chart schematically showing an example of the second release layer forming step. FIG. 8 is a partial cross-sectional side view schematically showing how a wafer moving along the X-axis direction is irradiated with a laser beam. FIG. 9 is a cross-sectional view schematically showing adjacent release layers formed inside the ingot. Each of FIGS. 10A and 10B is a partial cross-sectional side view schematically showing how the wafer is separated. FIG. 11 is a partial cross-sectional side view schematically showing how a rotating wafer is irradiated with a laser beam. FIG. 12 is a graph showing the width of the peeling layer formed inside the wafer when linear regions along different crystal orientations are irradiated with laser beams. FIG. 13 is a top view schematically showing a modification of the wafer. Each of FIGS. 14A and 14B is a partial cross-sectional side view schematically showing how a region in which a plurality of devices are formed and a peripheral region of a wafer are separated. Each of FIGS. 15A and 15B is a partial cross-sectional side view schematically showing how the front side and the back side of the wafer are separated.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1A is a top view schematically showing an example of a wafer (single crystal silicon wafer), and FIG. 1B is a cross-sectional view schematically showing an example of a wafer (single crystal silicon wafer). be. Note that FIG. 1A also shows the crystal orientation of the single-crystal silicon forming this wafer.

The wafer 11 shown in FIGS. 1(A) and 1(B) has a specific crystal plane included in the crystal plane {100} (here, for convenience, the crystal plane (100)) is a front surface 11a and a back surface. 11b is made of cylindrical single-crystal silicon exposed. That is, the wafer 11 is made of columnar single-crystal silicon in which the perpendiculars (crystal axes) to the front surface 11a and the back surface 11b are along the crystal orientation [100].

The wafer 11 is manufactured so that the crystal plane (100) is exposed on each of the front surface 11a and the back surface 11b. The surface may be slightly inclined from the surface (100). Specifically, each of the front surface 11a and the back surface 11b of the wafer 11 may be a plane having an acute angle of 1° or less with the crystal plane (100).

That is, the crystal axis of the wafer 11 may be along a direction with an acute angle of 1° or less with respect to the [100] crystal orientation. In addition, a notch 13 is formed in the side surface 11c of the wafer 11, and a specific crystal plane included in the crystal orientation <110> viewed from the notch 13 (here, for convenience, the crystal orientation is [011]). The center of the wafer 11 is located.

Further, the wafer 11 is partitioned into a plurality of regions by a plurality of dividing lines crossing each other, and ICs (Integrated Circuits) and LSIs (Large Scale Integration), semiconductor memories or CMOS (Complementary Metal Oxide Semiconductor) A device 15 such as an image sensor is formed.

Further, grooves in which TSVs are provided may be formed on the surface 11a side of the wafer 11 . Also, the outer peripheral region of the wafer 11 is chamfered. That is, the side surface 11c of the wafer 11 is curved so as to protrude outward. Note that the device 15 is not formed in the outer peripheral region of the wafer 11 . That is, the area of the wafer 11 where the devices 15 are formed is surrounded by the outer peripheral area.

FIG. 2 is a flow chart schematically showing an example of a wafer processing method. Briefly, in this method, the formed focal point is positioned inside the wafer 11, and the wafer 11 is irradiated with a laser beam having a wavelength that passes through the wafer 11, so that the laser beam is irradiated inside the wafer 11. After the separation layer is formed, the wafer 11 is separated using this separation layer as a separation starting point.

Specifically, in this method, first, the front surface 11a side of the wafer 11 is bonded to the front surface side of the support wafer (bonding step: S1). FIG. 3 is a cross-sectional view schematically showing how the front surface 11a side of the wafer 11 is attached to the front surface side of the support wafer. A support wafer 17 to be bonded to the wafer 11 has the same shape as the wafer 11, for example.

This support wafer 17 may be made of single crystal silicon, like the wafer 11, and may have a plurality of devices formed on its front surface 17a. Further, the surface 17a of the support wafer 17 is provided with an adhesive 19 such as an acrylic adhesive or an epoxy adhesive.

Then, in the bonding step ( S<b>1 ), the front surface 11 a of the wafer 11 is pressed against the front surface 17 a of the support wafer 17 via the adhesive 19 while supporting the back surface 17 b side of the support wafer 17 . As a result, a bonded wafer in which the surface 11a side of the wafer 11 is bonded to the surface 17a side of the support wafer 17 is formed.

Next, a release layer is formed inside the wafer 11 using a laser processing apparatus. FIG. 4 is a perspective view schematically showing an example of a laser processing apparatus used for forming a release layer inside the wafer 11. As shown in FIG. Note that the X-axis direction (horizontal direction) and the Y-axis direction (front-rear direction) shown in FIG. It is a direction (vertical direction) orthogonal to each of the axial directions.

A laser processing apparatus 2 shown in FIG. 4 has a base 4 that supports each component. A horizontal movement mechanism 6 is arranged on the upper surface of the base 4 . The horizontal movement mechanism 6 has a pair of Y-axis guide rails 8 fixed to the upper surface of the base 4 and extending along the Y-axis direction.

A Y-axis moving plate 10 is connected to the upper surface side of the pair of Y-axis guide rails 8 so as to be slidable along the pair of Y-axis guide rails 8 . A screw shaft 12 extending along the Y-axis direction is arranged between the pair of Y-axis guide rails 8 . A motor 14 for rotating the screw shaft 12 is connected to the front end (one end) of the screw shaft 12 .

A nut portion (not shown) for accommodating balls rolling on the surface of the rotating screw shaft 12 is provided on the surface of the screw shaft 12 on which the spiral grooves are formed, thereby forming a ball screw. That is, when the screw shaft 12 rotates, the balls circulate in the nut portion and the nut portion moves along the Y-axis direction.

Furthermore, this nut portion is fixed to the lower surface side of the Y-axis moving plate 10 . Therefore, when the screw shaft 12 is rotated by the motor 14, the Y-axis moving plate 10 moves along the Y-axis direction together with the nut portion. A pair of X-axis guide rails 16 extending along the X-axis direction are fixed to the upper surface of the Y-axis moving plate 10 .

An X-axis moving plate 18 is connected to the upper surface side of the pair of X-axis guide rails 16 in a manner slidable along the pair of X-axis guide rails 16 . A screw shaft 20 extending along the X-axis direction is arranged between the pair of X-axis guide rails 16 . A motor 22 for rotating the screw shaft 20 is connected to one end of the screw shaft 20 .

A nut portion (not shown) for accommodating balls rolling on the surface of the rotating screw shaft 20 is provided on the surface of the screw shaft 20 where the helical groove is formed, thereby forming a ball screw. That is, when the screw shaft 20 rotates, the balls circulate in the nut portion and the nut portion moves along the X-axis direction.

Furthermore, this nut portion is fixed to the lower surface side of the X-axis moving plate 18 . Therefore, when the screw shaft 20 is rotated by the motor 22, the X-axis moving plate 18 moves along the X-axis direction together with the nut portion.

A columnar table base 24 is arranged on the upper surface side of the X-axis movement plate 18 . A holding table 26 for holding the above-described bonded wafer is arranged above the table base 24 . The holding table 26 has, for example, a circular upper surface (holding surface) parallel to the X-axis direction and the Y-axis direction, and the porous plate 26a is exposed on this holding surface.

A rotary drive source (not shown) such as a motor is connected to the lower portion of the table base 24 . When the rotary drive source operates, the holding table 26 rotates about a straight line passing through the center of the holding surface and parallel to the Z-axis direction as a rotation axis. Moreover, when the above-described horizontal movement mechanism 6 operates, the holding table 26 moves along the X-axis direction and/or the Y-axis direction.

Furthermore, the porous plate 26a communicates with a suction source (not shown) such as a vacuum pump through a channel or the like provided inside the holding table 26. As shown in FIG. When this suction source operates, a negative pressure is generated in the space near the holding surface of the holding table 26 .

A support structure 30 having side surfaces substantially parallel to the Y-axis direction and the Z-axis direction is provided on the area behind the base 4 . A vertical movement mechanism 32 is arranged on the side surface of the support structure 30 . The vertical movement mechanism 32 has a pair of Z-axis guide rails 34 fixed to the side surface of the support structure 30 and extending along the Z-axis direction.

A Z-axis movement plate 36 is connected to the surface side of the pair of Z-axis guide rails 34 in a manner slidable along the pair of Z-axis guide rails 34 . A screw shaft (not shown) extending along the Z-axis direction is arranged between the pair of Z-axis guide rails 34 . A motor 38 for rotating the screw shaft is connected to the upper end (one end) of the screw shaft.

A nut portion (not shown) for accommodating balls rolling on the surface of the rotating screw shaft is provided on the surface of the screw shaft on which the helical groove is formed, thereby forming a ball screw. That is, when the screw shaft rotates, the balls circulate in the nut portion and the nut portion moves along the Z-axis direction.

Furthermore, this nut portion is fixed to the back side of the Z-axis moving plate 36 . Therefore, when the screw shaft arranged between the pair of Z-axis guide rails 34 is rotated by the motor 38, the Z-axis moving plate 36 moves along the Z-axis direction together with the nut portion.

A support 40 is fixed to the surface side of the Z-axis moving plate 36 . This support 40 supports a part of the laser beam irradiation unit 42 . FIG. 5 is a diagram schematically showing how the laser beam LB travels in the laser beam irradiation unit 42. As shown in FIG. 5, some of the constituent elements of the laser beam irradiation unit 42 are shown as functional blocks.

The laser beam irradiation unit 42 has a laser oscillator 44 fixed to the base 4 . The laser oscillator 44 has, for example, Nd:YAG as a laser medium, and emits a laser beam LB having a wavelength (for example, 1342 nm) that passes through the wafer 11 . This laser beam LB is, for example, a pulsed laser beam with a frequency of 60 kHz.

The laser beam LB is then supplied to the spatial light modulator 48 after its output has been adjusted in the attenuator 46 . The spatial light modulator 48 splits the laser beam LB. For example, the spatial light modulator 48 determines the position (coordinates) of the laser beam LB emitted from the irradiation head 52 (to be described later) on a plane (XY coordinate plane) parallel to the X-axis direction and the Y-axis direction and/or The laser beam LB adjusted in the attenuator 46 is branched so as to form a plurality of condensing points with mutually different positions (heights).

Also, the laser beam LB branched by the spatial light modulator 48 is reflected by the mirror 50 and guided to the irradiation head 52 . The irradiation head 52 houses a condensing lens (not shown) for condensing the laser beam LB. Then, the laser beam LB condensed by this condensing lens is emitted to the holding surface side of the holding table 26 .

As shown in FIG. 4, the irradiation head 52 is provided at the front end of a cylindrical housing 54. As shown in FIG. A support 40 is fixed to the rear side surface of the housing 54 . Furthermore, an imaging unit 56 is fixed to the front side surface of the housing 54 .

The imaging unit 56 has, for example, a light source such as an LED (Light Emitting Diode), an objective lens, and an imaging element such as a CCD (Charge Coupled Device) image sensor or a CMOS image sensor.

Then, when the vertical movement mechanism 32 described above operates, the laser beam irradiation unit 42 and the imaging unit 56 move along the Z-axis direction. Furthermore, a cover (not shown) is provided on the base 4 to cover the components described above. A touch panel 58 is arranged on the front surface of this cover.

The touch panel 58 includes, for example, an input device such as a capacitive or resistive touch sensor and a display device such as a liquid crystal display or an organic EL (Electro Luminescence) display, and functions as a user interface.

When forming the release layer inside the wafer 11 using the laser processing apparatus 2, first, the center of the holding surface of the holding table 26 and the center of the back surface 17b of the support wafer 17 are aligned so that they are bonded together. A wafer is placed on the holding table 26 . A suction source communicating with the holding table 26 is then operated such that the bonded wafer is held by the holding table 26 .

Next, the imaging unit 56 images the rear surface 11b side of the wafer 11 of the bonded wafer to form an image. Next, referring to this image, the horizontal movement mechanism 6 is operated so that the irradiation head 52 of the laser beam irradiation unit 42 is positioned just above the area slightly inside the outer peripheral area of the wafer 11 .

Further, referring to this image, the holding table 26 is rotated so that the crystal orientation [010] of the single crystal silicon constituting the wafer 11 becomes parallel to the X-axis direction, and the crystal orientation [001] becomes parallel to the Y-axis direction. A rotary drive source connected to the lower portion of the table base 24 may be operated so as to be parallel to .

Next, by irradiating the laser beam LB to the annular first region inside the outer peripheral region of the wafer 11, the region where the plurality of devices 15 are formed and the outer peripheral region of the wafer 11 are separated. A first release layer serving as a starting point is formed (first release layer forming step: S2).

In this first release layer forming step (S2), the wafer 11 is held via the support wafer 17 while the laser beam LB is applied to the annular first region inside the outer peripheral region of the wafer 11. The holding table 26 is rotated. FIG. 6 is a partial cross-sectional side view schematically showing how the rotating wafer 11 is irradiated with the laser beam LB.

Specifically, in the first release layer forming step (S2), a plurality of (for example, 2 to 10) condensing points having different positions (heights) in the Z-axis direction are formed. The wafer 11 is irradiated with the laser beam LB branched into .

The plurality of condensing points are positioned so that, for example, the lowest condensing point is positioned slightly higher than the surface 11a of the wafer 11, and the uppermost condensing point is located above the surface 11a of the wafer 11. and the back surface 11b. Also, the plurality of condensing points are arranged, for example, so that the positions (heights) in the Z-axis direction are evenly spaced (for example, every 5 μm to 15 μm).

In this case, a modified region 21 having a disordered crystal structure is formed inside the wafer 11 around each of the plurality of condensing points. Furthermore, cracks 23 extend from each of the plurality of modified regions 21 so as to connect a pair of adjacent modified regions 21 .

As a result, a peel layer including a plurality of modified regions 21 and cracks 23 extending from each of the plurality of modified regions 21 is formed inside the wafer 11 . Next, while irradiating the laser beam LB onto the wafer 11, the rotary drive source connected to the lower part of the table base 24 is operated so as to rotate the holding table 26 holding the bonded wafer once.

As a result, a peeling layer (first peeling layer) is formed between the region of the wafer 11 where the devices 15 are formed and the peripheral region. This first peeling layer has, for example, a cylindrical shape along the side of a column whose lower bottom surface is located on the surface 11 a side of the wafer 11 and whose upper bottom surface is located inside the wafer 11 .

Next, by irradiating a second region inside the outer peripheral region of the wafer 11 with a laser beam LB, a second release layer that serves as a separation starting point between the front surface 11a side and the back surface 11b side of the wafer 11 is formed. is formed (second release layer forming step: S3). FIG. 7 is a flow chart schematically showing an example of the second release layer forming step (S3).

In the second separation layer forming step (S3), first, a linear region along the crystal orientation [010] of the single crystal silicon constituting the wafer 11 is irradiated with a laser beam LB (laser beam irradiation step: S31). For example, when the bonded wafer is held by the holding table 26 with the crystal orientation [010] parallel to the X-axis direction, the holding table 26 is moved along the X-axis direction while the wafer 11 is irradiated with the laser beam. A beam LB is emitted.

FIG. 8 is a partial cross-sectional side view schematically showing how the wafer 11 moving along the X-axis direction is irradiated with the laser beam LB. In this laser beam irradiation step (S31), for example, the laser beam LB branched so as to form a plurality of (for example, 2 to 10) condensing points with different positions (coordinates) in the Y-axis direction. is irradiated onto the wafer 11 .

The plurality of condensing points are positioned, for example, at the same height as the uppermost modified region 21 among the plurality of modified regions 21 included in the first peeling layer described above. Also, the plurality of condensing points are arranged, for example, so that the positions (coordinates) in the Y-axis direction are evenly spaced (for example, every 5 μm to 15 μm).

In this case, a plurality of modified regions 21 and cracks 23 extending from each of the plurality of modified regions 21 are formed inside the wafer 11, as in the first separation layer forming step (S2). Next, while the laser beam LB is being applied to the wafer 11, the horizontal movement mechanism 6 is operated to move the holding table 26 holding the bonded wafer along the X-axis direction.

As a result, the release layer 25 is formed in a linear region along the X-axis direction included in the second region inside the outer peripheral region of the wafer 11 . Here, most of the cracks 23 included in the peeling layer 25 extend along the crystal plane (k01) (k is an integer whose absolute value is 10 or less, excluding 0). That is, when the wafer 11 is irradiated with the laser beam LB in this manner, the crack 23 tends to extend in the following crystal planes.

The acute angle formed by the crystal plane (100) exposed on the front surface 11a and the back surface 11b of the wafer 11 and the crystal plane (k01) is 45° or less. Therefore, if the direction in which the crack 23 extends is decomposed into a component parallel (parallel component) and a component perpendicular (perpendicular component) to the front surface 11a and back surface 11b of the wafer 11, the parallel component is greater than or equal to the vertical component.

Next, the holding table 26 is moved along the crystal orientation [001] of the single crystal silicon forming the wafer 11 (indexing step (S32)). For example, when the bonded wafer is held by the holding table 26 with the crystal orientation [001] of the single crystal silicon forming the wafer 11 parallel to the Y-axis direction, the holding table 26 is moved along the Y-axis direction. to move.

Next, the laser beam irradiation unit 42 and the horizontal movement mechanism 6 are operated so that the peeling layer 25 is formed in a linear region parallel to the linear region where the peeling layer 25 has already been formed. That is, the laser beam irradiation step (S31) is performed again. FIG. 9 is a cross-sectional view schematically showing adjacent peeling layers 25 formed inside the wafer 11 by performing the laser beam irradiation step (S31) twice.

In this case, the release layer 25 (release layer 25-1) formed in the first laser beam irradiation step (S31) is parallel to the release layer 25 (release layer 25-1) and separated from the release layer 25-1 in the Y-axis direction. A release layer 25 - 2 ) is formed inside the wafer 11 . Further, the indexing feeding step (S32 ) and the laser beam irradiation step (S31) are repeated.

Then, when the release layer 25 is formed in the entire second region inside the outer peripheral region of the wafer 11 (step (S33): YES), the second release layer forming step (S3) is completed. As a result, a release layer (second release layer) is formed between the front surface 11a side and the back surface 11b side of the wafer 11 . This second release layer has, for example, a disk-like shape along the upper bottom surface of a cylinder having a side surface along the first release layer described above.

In the method shown in FIG. 2, after performing the first release layer forming step (S2) and the second release layer forming step (S3), by applying an external force to the wafer 11, the first release layer and The wafer 11 is separated using the second separation layer as a starting point of separation (separation step: S4).

10A and 10B are partial cross-sectional side views schematically showing how the wafer 11 is separated. This separation step (S4) is performed, for example, in a separation device 60 shown in FIGS. 10(A) and 10(B). This separating device 60 has a holding table 62 that holds bonded wafers including the wafer 11 on which the first and second peeling layers are formed.

The holding table 62 has a circular upper surface (holding surface), from which a porous plate (not shown) is exposed. Furthermore, this porous plate communicates with a suction source (not shown) such as a vacuum pump through a channel or the like provided inside the holding table 62 . When this suction source operates, a negative pressure is generated in the space near the holding surface of the holding table 62 .

A separation unit 64 is provided above the holding table 62 . This separation unit 64 has a cylindrical support member 66 . For example, a ball-screw elevating mechanism (not shown) is connected to the upper portion of the support member 66, and the separation unit 64 is elevated by operating the elevating mechanism.

The lower end of the support member 66 is fixed to the center of the upper portion of the disk-shaped grasping claw base 68 . A plurality of gripping claws 70 are provided at approximately equal intervals along the circumferential direction of the gripping claw base 68 below the outer peripheral region of the gripping claw base 68 . The gripping claw 70 is provided with a plate-like standing portion 70a extending downward.

The upper end of the standing portion 70a is connected to an actuator such as an air cylinder built in the gripping claw base 68. By operating this actuator, the gripping claws 70 move along the gripping claw base 68 in the radial direction. to move. Further, on the inner surface of the lower end portion of the standing portion 70a, a plate-shaped plate extending toward the center of the gripping claw base 68 and having a thickness that becomes thinner toward the center of the gripping claw base 68 is provided. A claw portion 70b is provided.

In the separation device 60, for example, the separation step (S4) is performed in the following order. Specifically, first, the center of the back surface 17b of the support wafer 17 of the bonded wafer including the wafer 11 on which the first release layer and the second release layer are formed is aligned with the center of the holding surface of the holding table 62. The bonded wafer is placed on the holding table 62 so as to allow the bonding to occur.

Then, the suction source communicating with the porous plate exposed at the holding surface is operated so that the bonded wafer is held by the holding table 62 . Next, the actuator is operated to position each of the plurality of gripping claws 70 radially outward of the gripping claw base 68 .

Next, the elevating mechanism is operated so that the tips of the claw portions 70b of the plurality of gripping claws 70 are positioned at a height corresponding to the adhesive 19 of the bonded wafer. Next, the actuator is operated so as to bring the claw portion 70b into contact with the bonded wafer. Next, the elevating mechanism is operated so as to elevate the claw portion 70b (see FIG. 10(A)).

As a result, an upward external force, that is, an external force along the thickness direction of the wafer 11 is applied to the outer peripheral region of the wafer 11 . As a result, the cracks 23 included in the first and second peeling layers are further extended to separate the peripheral region from the region where the plurality of devices 15 of the wafer 11 are formed, and The 11a side and the rear surface 11b side are separated (see FIG. 10B).

In the wafer processing method described above, the wafer 11 manufactured so that the crystal plane (100) is exposed on each of the front surface 11a and the back surface 11b is irradiated with a laser beam LB along the crystal orientation [010]. As a result, a peeling layer (second peeling layer) serving as a separation starting point between the front surface 11a side and the back surface 11b side of the wafer 11 is formed.

In this case, most of the cracks 23 extending from the modified region 21 are along the crystal plane (k01) (k is an integer whose absolute value is 10 or less, excluding 0). The acute angle formed by the crystal plane (100) and the crystal plane (k01) of single crystal silicon is 45° or less. Therefore, in this wafer processing method, the component (parallel component) parallel to the front surface 11a and back surface 11b of the wafer 11 in the direction in which the crack 23 extends is larger than the vertical component (perpendicular component).

Thus, in this wafer processing method, the interval between adjacent modified regions 21 can be lengthened. As a result, the moving distance (index) in the indexing feeding step (S42) can be lengthened, and the separation layer 25 necessary for forming the release layer 25 serving as the separation starting point between the front surface 11a side and the back surface 11b side of the wafer 11 can be increased. Processing time (irradiation time of laser beam LB) can be shortened.

Further, in this wafer processing method, the crack 23 is less likely to extend from the release layer 25 toward the surface 11a of the wafer 11 . As a result, the probability that the device 15 will be damaged when separating the front surface 11a side and the rear surface 11b side of the wafer 11 can be reduced.

Note that the above-described wafer processing method is one aspect of the present invention, and the present invention is not limited to the above-described method. For example, in the present invention, the surface 11a side of the wafer 11 may be bonded to the surface 17a side of the support wafer 17 after the first release layer and the second release layer are formed on the wafer 11 . That is, in the present invention, the bonding step (S1) may be performed after performing the first release layer forming step (S2) and the second release layer forming step (S3).

Moreover, the structure of the laser processing apparatus used in the present invention is not limited to the structure of the laser processing apparatus 2 described above. For example, the present invention is implemented using a laser processing apparatus provided with a horizontal movement mechanism for moving the irradiation head 52 of the laser beam irradiation unit 42 along each of the X-axis direction and/or the Y-axis direction. good too.

That is, in the present invention, the holding table 26 that holds the bonded wafer including the wafer 11 and the irradiation head 52 of the laser beam irradiation unit 42 that emits the laser beam LB are arranged along the X-axis direction and the Y-axis direction. As long as they can move relatively, there is no limitation on the structure for that purpose.

In addition, in the present invention, there is no limitation on before and after the first release layer forming step (S2) and the second release layer forming step (S3). That is, in the present invention, the first peeling layer forming step (S2) may be performed after the second peeling layer forming step (S3).

However, when the disc-shaped second release layer is formed inside the wafer 11 in the second release layer forming step (S3), the second release layer is newly separated on the surface 11a side of the wafer 11. Forming the layers may be impossible or difficult.

Therefore, in the present invention, it is preferable to carry out the second release layer formation step (S3) after carrying out the first release layer formation step (S2). This makes it possible to reliably form a peeling layer (first peeling layer) serving as a separation starting point between the region where the plurality of devices 15 are formed and the peripheral region of the wafer 11 .

Alternatively, in the present invention, it is preferable that the second region of the wafer 11 where the second release layer is formed is located inside the first region where the first release layer is formed. As a result, the first release layer can be reliably formed even when the first release layer formation step (S2) is performed after the second release layer formation step (S3) is performed. .

Further, in the first separation layer forming step (S2) of the present invention, a first separation layer is formed that can function as a starting point of separation between the region of the wafer 11 where the plurality of devices 15 are formed and the peripheral region. The shape of the first release layer is not limited as long as it is possible. For example, the first peeling layer may have a shape along the side surface of a cylinder whose lower bottom surface is located on the front surface 11a side of the wafer 11 and whose upper bottom surface is located on the back surface 11b side of the wafer 11 .

That is, the first release layer may be formed so as to penetrate the front surface 11 a and the back surface 11 b of the wafer 11 . However, if the first peeling layer has such a shape, there is a risk that the outer peripheral region of the wafer 11 will scatter as offcuts in the separation step (S4). Therefore, in the first release layer forming step (S2) of the present invention, it is preferable to form the first release layer so as not to reach the back surface 11b of the wafer 11. FIG.

The first release layer has a lower bottom surface (first bottom surface) located on the surface 11a side of the wafer 11 and an upper bottom surface (second bottom surface) having a smaller diameter than the lower bottom surface inside the wafer 11. It may be shaped along the side of a truncated cone located at . Such a first peeling layer is formed, for example, by irradiating the wafer 11 with the laser beam LB such that the formed focal point is closer to the surface 11a of the wafer 11 as it approaches the outer peripheral region.

FIG. 11 is a partial cross-sectional side view schematically showing how the rotating wafer 11 is irradiated with the laser beam LB in order to form the first release layer having such a shape. Specifically, when forming such a first peeling layer, first, adjacent The wafer 11 is irradiated with a laser beam LB that forms a plurality of (e.g., eight) condensing points with the positions of the condensing points shifted by 10 μm inside the wafer 11 .

In this case, a modified region 21 in which the crystal structure of the material forming the wafer 11 is disturbed is formed inside the wafer 11 around each of the plurality of converging points. That is, a plurality of modified regions 21 are formed so as to line up in a straight line along the radial direction of the wafer 11 in plan view and form an acute angle of 45° between the straight line and the surface 11a of the wafer 11. be.

The acute angle formed by the plurality of linearly aligned modified regions 21 and the surface 11a of the wafer 11 is not limited to 45°. That is, the wafer 11 may be irradiated with the laser beam LB so that a plurality of condensing points are formed in which the distance between adjacent condensing points in the radial direction of the wafer 11 is different from the distance in the thickness direction thereof.

Furthermore, cracks 23 extend from each of the plurality of modified regions 21 so as to connect a pair of adjacent modified regions 21 . As a result, a peel layer including a plurality of modified regions 21 and cracks 23 extending from each of the plurality of modified regions 21 is formed inside the wafer 11 .

Next, while the laser beam irradiation unit 42 is being operated, the rotary drive source connected to the lower part of the table base 24 is operated so as to rotate the holding table 26 holding the bonded wafers once.

As a result, a peeling layer (first peeling layer) along the side surface of a truncated cone having a lower bottom surface located on the surface 11 a side of the wafer 11 and an upper bottom surface located inside the wafer 11 is formed on the outer periphery of the wafer 11 . It is formed in the annular first region inside the region.

When such a first separation layer is formed, when the wafer 11 is separated by the separation device 60 described above, the side surface of the region where the plurality of devices 15 are newly exposed and the outer peripheral region are exposed. The probability that the inner surfaces come into contact with each other is reduced. Also, in this case, the crack 23 tends to extend from the first release layer in the direction along the side surface of the truncated cone.

Therefore, in this case, the probability of the crack 23 extending toward the device 15 is also low, and damage to the device 15 can be suppressed. Furthermore, when such a first peeling layer is formed, it becomes easy to manufacture chips by utilizing the region of the surface 11a of the wafer 11 close to the outer peripheral region. Therefore, in this case, the number of chips that can be manufactured from the wafer 11 can be increased.

Further, in the first peeling layer forming step (S2) of the present invention, the horizontal movement mechanism 6 and the vertical movement mechanism 32 are operated in addition to or instead of the rotary drive source connected to the lower part of the table base 24. The wafer 11 may be irradiated with the laser beam LB while the wafer 11 is being heated. In other words, the wafer 11 may be irradiated with the laser beam LB while not only rotating the wafer 11 but also changing the coordinates and height of the focal point on the XY coordinate plane.

Further, in the first release layer forming step (S2) of the present invention, the laser beams LB may be irradiated a plurality of times in which the positions of the focal points are the same or close to each other. In this case, the size of the modified region 21 included in the peel layer increases, and the crack 23 included in the peel layer further extends. Therefore, in this case, separation of the wafer 11 in the separation step (S4) is facilitated.

In addition, in the first release layer forming step (S2) of the present invention, the laser beam LB is applied to the wafer 11 so that the adjacent modified regions 21 are not connected through the cracks 23 but directly connected to each other. may be irradiated. In this case, the shape of the peeling layer can be determined without depending on the shape of the crack 23 that develops from the modified region 21, so that the wafer 11 can be processed stably.

Further, the region irradiated with the laser beam LB in the laser beam irradiation step (S31) of the second separation layer forming step (S3) of the present invention is along the crystal orientation [010] of the single crystal silicon constituting the wafer 11. is not limited to a linear region. For example, in this laser beam irradiation step (S31), a linear region along the crystal orientation [001] may be irradiated with the laser beam LB.

In addition, when the laser beam LB is irradiated to the wafer 11 in this way, the crack 23 tends to extend in the following crystal planes.

Furthermore, in the present invention, the laser beam LB may be applied to a linear region along a direction slightly inclined from the crystal orientation [010] or the crystal orientation [001] in plan view. This point will be described with reference to FIG.

FIG. 12 shows the width of the peeling layer formed inside the wafer 11 when linear regions along different crystal orientations are irradiated with the laser beam LB (perpendicular to the direction in which the linear regions extend). is a graph showing the length of the direction). The horizontal axis of this graph represents the direction in which a linear region (reference region) perpendicular to the crystal orientation [011] extends and the linear region to be measured (measurement region) in plan view. It shows the angle formed with the existing direction.

That is, when the value of the horizontal axis of this graph is 45°, the linear region along the crystal orientation [001] is the object of measurement. Similarly, when the value of the horizontal axis of this graph is 135°, the linear region along the crystal orientation [010] is the object of measurement. The vertical axis of this graph represents the width of the separation layer formed in the measurement region by irradiating the laser beam LB to the measurement region, and the width of the separation layer formed in the reference region by irradiating the laser beam LB to the reference region. It shows the value when divided by the width of the layer.

As shown in FIG. 12, the width of the release layer is 40° to 50° or 130° to 140° when the angle formed by the direction in which the reference region extends and the direction in which the measurement region extends. get wider. That is, the width of the peeling layer is not limited to the crystal orientation [001] or the crystal orientation [010]. becomes wider when irradiated with

Therefore, in the laser beam irradiation step (S31) of the second release layer forming step (S3) of the present invention, along a direction inclined by 5° or less from the crystal orientation [001] or the crystal orientation The linear region may be irradiated with the laser beam LB.

That is, in this laser beam irradiation step (S31), among the specific crystal planes included in the crystal plane {100}, the crystal planes exposed on the front surface 11a and the back surface 11b of the wafer 11 (here, the crystal plane (100 )) parallel to the crystal orientation <100> and making an angle of 5° or less with respect to a specific crystal orientation (here, crystal orientation [001] or crystal orientation [010]) included in the crystal orientation <100> ( A linear region along the first direction) may be irradiated with the laser beam LB.

Further, when the laser beam irradiation step (S31) is carried out in this way, the indexing feeding step (S32) is performed by the front surface 11a and the rear surface 11b of the wafer 11 among the specific crystal planes included in the crystal plane {100}. Condensed by irradiation of the laser beam LB along a direction (second direction) parallel to the crystal plane (here, crystal plane (100)) exposed to each of This is done by moving the position inside the wafer 11 where the points are formed.

In addition, in the second release layer forming step (S3) of the present invention, the entire second region inside the outer peripheral region of the wafer 11 (from the region on the one end side in the Y-axis direction to the region on the other end side) ) After the peeling layer 25 is formed (step S33: YES), the laser beam irradiation step (S31) and the indexing feeding step (S32) may be repeated.

That is, the second region where the separation layer 25 has already been formed may be again irradiated with the laser beam LB so as to form the separation layer 25 . In this case, the respective densities of the modified regions 21 and the cracks 23 included in the peeling layer 25 are increased. This facilitates separation of the wafer 11 in the separation step (S4).

Further, in the second release layer forming step (S3) of the present invention, the laser beam irradiation step (S31) is performed again after the laser beam irradiation step (S31) and before the indexing and feeding step (S32). may be implemented. That is, the laser beam LB may be applied again to form the peeling layer 25 on the linear region where the peeling layer 25 has already been formed. In this case, the separation of the wafers in the separation step (S4) is facilitated in the same manner as described above.

Further, in the separation step (S4) of the present invention, ultrasonic waves may be applied to the wafer 11 prior to the separation of the wafer 11 on which the first separation layer and the second separation layer are formed. In this case, the cracks 23 included in the first and second peeling layers are extended, so that the wafer 11 can be easily separated.

Moreover, in the separation step (S4) of the present invention, the wafer 11 may be separated using a device other than the separation device 60 described above. For example, in the separation step (S4) of the present invention, after separating the region where the plurality of devices 15 are formed and the peripheral region of the wafer 11, the front surface 11a side and the rear surface 11b side of the wafer 11 are separated. good too.

An example of such a separation step (S4) will be described below with reference to FIGS. 13 to 15. FIG. FIG. 13 is a top view schematically showing the wafer 11 subjected to such separation step (S4). A plurality of notches 11d each extending along the radial direction of the wafer 11 are formed in the outer peripheral region of the wafer 11 prior to the bonding step (S1) described above.

The plurality of cutouts 11d are formed at approximately equal intervals along the circumferential direction of the wafer 11, except for the portions where the notches 13 are formed. Each of the plurality of cutouts 11d is formed so that the radially inner portion of the wafer 11 reaches the first peeling layer formed in the first peeling layer forming step (S2) described above.

The first release layer formed inside the wafer 11 has a lower bottom surface located on the front surface 11a side of the wafer 11 and an upper bottom surface located on the back surface 11b side of the wafer 11. It has a shape like That is, in this wafer 11, the first release layer is formed so as to penetrate the front surface 11a and the back surface 11b of the wafer 11. As shown in FIG.

Note that the plurality of notches 11d are formed by cutting the wafer 11 with a known cutting device, for example. Alternatively, the plurality of notches 11d may be formed by irradiating the wafer 11 with a laser beam that causes laser ablation in a known laser processing apparatus.

Furthermore, in the outer peripheral region of the wafer 11, a plurality of release layers each extending along the radial direction of the wafer 11 may be formed in the outer peripheral region of the wafer 11 instead of the plurality of cutouts 11d. This release layer is formed, for example, by a method similar to the method for forming the first release layer and the second release layer described above.

14(A) and 14(B) are partial cross-sectional side views schematically showing how a region in which a plurality of devices 15 are formed and an outer peripheral region of the wafer 11 shown in FIG. 13 are separated. It is a diagram. This separation of the wafer 11 is performed using an expansion device 72 shown in FIGS. 14(A) and 14(B).

This expansion device 72 has a cylindrical drum 74 which is fixed. A support unit 76 is provided around the drum 74 . The support unit 76 has an annular support 78 surrounding the upper end of the drum 74 . A plurality of clamps 80 are provided on the support base 78 at approximately equal intervals along the circumferential direction of the support base 78 .

In addition, a plurality of air cylinders are provided below the support base 78 at approximately equal intervals along the circumferential direction of the support base 78, and the upper end of the piston rod 82 of each air cylinder is fixed to the lower part of the support base 78. It is Therefore, in the expansion device 72, the support base 78 and the plurality of clamps 80 can be raised and lowered together with the piston rod 82 by operating the plurality of air cylinders.

When separating the area where the plurality of devices 15 are formed and the outer peripheral area of the wafer 11 shown in FIG. Also, the rear surface 11b of the wafer 11 is attached to the central region. Thereby, a frame unit is formed in which the bonded wafer obtained by bonding the wafer 11 and the support wafer 17 and the annular frame 29 are integrated.

Next, a plurality of air cylinders are operated so that the upper surface of the support table 78 is positioned flush with the upper end of the drum 74 . Next, the annular frame 29 is placed on the support table 78 with the expanding tape 27 interposed therebetween. That is, the frame unit is placed on the support stand 78 so that the support wafer 17 faces upward.

Next, the annular frame 29 is fixed by a plurality of clamps 80 (see FIG. 14(A)). A plurality of air cylinders are then operated to lower the annular frame 29 fixed by the plurality of clamps 80 . As a result, the central region of the expanding tape 27 is expanded along the radial direction of the wafer 11 by the amount that the annular frame 29 is lowered.

At this time, a force directed radially outward of the wafer 11 acts on the wafer 11 attached to the expanding tape 27 . As a result, the region where the plurality of devices 15 are formed and the peripheral region of the wafer 11 are separated from each other with the first separation layer serving as a starting point of separation (see FIG. 14B).

15A and 15B are partial cross-sectional side views schematically showing how the front surface 11a side and the back surface 11b side of the wafer 11 shown in FIG. 14B are separated. . This separation of the wafer 11 is performed using a separation device 84 shown in FIGS. 15(A) and 15(B). This separating device 84 has a holding table 86 that holds bonded wafers including the wafer 11 shown in FIG. 14(B).

The holding table 86 has a circular upper surface (holding surface), from which a porous plate (not shown) is exposed. Furthermore, this porous plate communicates with a suction source (not shown) such as a vacuum pump through a channel or the like provided inside the holding table 86 . Therefore, when this suction source operates, a negative pressure is generated in the space near the holding surface of the holding table 86 .

A separation unit 88 is provided above the holding table 86 . This separation unit 88 has a cylindrical support member 90 . For example, a ball-screw elevating mechanism (not shown) is connected to the upper portion of the support member 90, and the separating unit 88 is elevated by operating the elevating mechanism.

A disk-shaped suction plate 92 is fixed to the center of the upper portion of the lower end of the support member 90 . A plurality of suction ports are formed on the lower surface of the suction plate 92 , and each of the plurality of suction ports is connected to a suction source (not shown) such as a vacuum pump via a channel or the like provided inside the suction plate 92 . communicates with Therefore, when this suction source operates, a negative pressure is generated in the space near the lower surface of the suction plate 92 .

When separating the front surface 11a side and the back surface 11b side of the wafer 11 shown in FIG. Next, the bonded wafer is placed on the holding table 86 so that the center of the back surface 17b of the support wafer 17 of this bonded wafer and the center of the holding surface of the holding table 86 are aligned.

A suction source communicating with the porous plate exposed at the holding surface is then operated so that the bonded wafer is held by the holding table 86 . Next, the lifting mechanism is operated to lower the separation unit 88 so that the lower surface of the suction plate 92 is brought into contact with the back surface 11b of the wafer 11 .

Next, the suction source communicating with the plurality of suction ports formed in the suction plate 92 is operated so that the back surface 11b side of the wafer 11 is suctioned through the plurality of suction ports. Next, the lifting mechanism is operated to lift the separation unit 88 so as to separate the suction plate 92 from the holding table 86 (see FIG. 15A).

At this time, an upward force along the thickness direction of the wafer 11 acts on the wafer 11 whose rear surface 11b side is sucked through a plurality of suction ports formed in the suction plate 92 . As a result, the front surface 11a side and the rear surface 11b side of the wafer 11 are separated from each other with the second release layer serving as a starting point of separation (see FIG. 15B).

In addition, the structure, method, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention.

11: Wafer (11a: front surface, 11b: back surface, 11c: side surface, 11d: notch)
13: notch 15: device 17: support wafer (17a: front surface, 17b: back surface)
19: Adhesive 21: Modified region 23: Crack 25 (25-1, 25-2): Release layer 27: Expanding tape 29: Annular frame 2: Laser processing device 4: Base 6: Horizontal movement mechanism 8: Y Axis guide rail 10: Y-axis moving plate 12: Screw shaft 14: Motor 16: X-axis guide rail 18: X-axis moving plate 20: Screw shaft 22: Motor 24: Table base 26: Holding table (26a: porous plate)
30: Support structure 32: Vertical movement mechanism 34: Z-axis guide rail 36: Z-axis movement plate 38: Motor 40: Support 42: Laser beam irradiation unit 44: Laser oscillator 46: Attenuator 48: Spatial light modulator 50: Mirror 52: Irradiation head 54: Housing 56: Imaging unit 58: Touch panel 60: Separating device 62: Holding table 64: Separating unit 66: Supporting member 68: Gripping claw base 70: Grasping claw (70a: standing portion, 70b: claw)
72: Expansion device 74: Drum 76: Support unit 78: Support base 80: Clamp 82: Piston rod 84: Separation device 86: Holding table 88: Separation unit 90: Support member 92: Suction plate

Claims (5)

Single-crystal silicon manufactured so that specific crystal planes included in the crystal plane {100} are exposed on each of the front and back surfaces, a plurality of devices are formed on the front surface side, and the peripheral region is chamfered By irradiating the wafer with a laser beam having a wavelength that passes through the single crystal silicon, the focal point formed is positioned inside the single crystal silicon wafer. A single crystal silicon wafer processing method for forming a separation layer and then separating the single crystal silicon wafer using the separation layer as a separation starting point, comprising:
a bonding step of bonding the surface side of the single crystal silicon wafer to the surface side of a support wafer;
By irradiating the laser beam from the rear surface side of the single crystal silicon wafer to the annular first region inside the outer peripheral region of the single crystal silicon wafer, the plurality of single crystal silicon wafers are a first release layer forming step of forming a first release layer serving as a separation starting point between the region where the device of is formed and the peripheral region;
By irradiating the laser beam from the back surface side of the single crystal silicon wafer to the second region inside the outer peripheral region of the single crystal silicon wafer, the front surface side of the single crystal silicon wafer and the a second release layer forming step of forming a second release layer that serves as a starting point for separation from the back side;
After performing the bonding step, the first release layer forming step and the second release layer forming step, the first release layer and the second release layer are separated by applying an external force to the single crystal silicon wafer. a separation step of separating the single crystal silicon wafer using the separation layer of
In the second release layer forming step,
The single crystal silicon wafer and the collection along a first direction parallel to the specific crystal plane and forming an angle of 5° or less with respect to the specific crystal orientation included in the crystal orientation <100>. a laser beam irradiation step of irradiating a linear region along the first direction included in the second region with the laser beam while relatively moving the light spot;
inside the single crystal silicon wafer where the focal point is formed by irradiation of the laser beam along a second direction parallel to the specific crystal plane and orthogonal to the first direction an indexing feed step for moving the position;
is repeatedly performed to form the second release layer. 2. The method of processing a wafer according to claim 1, wherein said first peeling layer forming step is performed before said second peeling layer forming step is performed. 3. The method of processing a wafer according to claim 1, wherein the second area is located inside the first area. 4. The method according to any one of claims 1 to 3, wherein in said first separation layer forming step, said first separation layer is formed so as not to reach said back surface of said single crystal silicon wafer. Wafer processing method. In the first peeling layer forming step, by irradiating the laser beam so that the formed focal point is closer to the surface of the single crystal silicon wafer as it is closer to the peripheral region, the first separation layer is formed. The bottom surface is located on the surface side of the single crystal silicon wafer, and the second bottom surface having a smaller diameter than the first bottom surface is along the side surface of the truncated cone located inside the single crystal silicon wafer. 5. The method of processing a wafer according to claim 1, wherein said second release layer is formed.

Images